There has long been a need for disinfecting medical instruments between applications to the body, particularly in sensitive areas, e.g. the eyes, in order to prevent transmission of disease causing bacteria and viruses. Recent isolation of immunodeficiency virus from tears of patients with AIDS and the isolation of Herpes Simplex virus type one, Hepatitis B virus and Adenovirus has heightened interest in the transmission of these diseases. Herpes Simplex Viral eye disease is a leading cause of corneal blindness in the United States and other industrialized nations, as well as developing countries throughout the world. Herpetic eye disease in the United States occurs in about one half million people per year. Ten million people are estimated to be affected annually worldwide and several million people are visually impaired as a result of Herpetic eye disease. Trachoma, caused by a chlamydial organism is a chronic and progressive infectious disease which is the world's leading cause of preventable blindness. It is a potential contaminant of ocular instruments worldwide.
Bacteria such as Staphylococcus, Pseudomonas, Bacillus, Pneumococci and Acanthamoeba are serious causes of ocular infections. Common fungi such as Fusarium Solani, Aspergillus Fumigatus and Candida Albicans contribute to a large number of fungal infections. All are potential agents for contaminating ocular instruments during routine examinations.
There is increased pathogenic flora in contact lens wearers, thus raising the potential for instrument contamination whenever such patients are being examined. The number of reported cases of Acanthamoeba Keratitis has increased dramatically in recent years. These organisms are known to exhibit a propensity to adhere to the walls of plastic containers, thereby being potential contaminants in ophthalmological settings.
The American Academy of Ophthalmology recommends soaking tonometer heads in a dilute Clorox solution. Alcide Corporation developed a two compound product called Exspor that has to be mixed and then diluted. This chlorous acid based chemical sterilizes within three minutes and disinfects spores only after the disinfected article is soaked in the solution for six hours. Another commonly used disinfectant is three percent hydrogen peroxide. It destroys spores when the disinfected article is soaked for four hours. An alternate agent is seventy percent isopropyl alcohol wipes, recommended for preventing possible transmission of viruses from tears, via tonometers.
Present methods for disinfecting non metallic ocular instruments are cumbersome and time consuming both in preparation and implementation. The chemical solutions used are toxic and in some cases require special precautions in order to prevent any potential risk of chemical residue getting into the eye. For example, fluffy white corneal lesion was seen in a patient immediately after applanation tonometry. The tonometer applanation surface had been disinfected with peroxide solution overnight. Slit-lamp examination revealed a circular corneal epithelial defect corresponding in size to the tonometer applanation surface. In another case, damage to the cornea was a result of wiping the tonometer with seventy percent isopropyl alcohol. After using the applanation tonometer, slit-lamp examination of a thirty-eight year old woman with type I diabetes mellitus revealed a circular area of corneal epithelial opacification corresponding to the size of the tonometer applanation surface.
Disinfection systems are needed, not only for medical instruments, but for other objects, metallic and non-metallic, which are used in environments where infectious organisms are concentrated and where such organisms are likely to come into human contact or even be ingested or inspired by humans.
Current disinfection systems use chemicals which are toxic to the environment, heat, ultra-violet light, X-rays and other radiation which can be physically damaging. What is needed is a disinfection system which employs a disinfection agent that is normally benign but can be selectively rendered active for attacking and killing infectious organisms.